High frequency miniature coaxial connectors are typically used for transmitting and delivering high frequency signals, typically in the range of 3 MHz to 300 GHz, from one medium to another. One example of such connectors, and also one of the most widely used in the industry, is known as the N connector.
There are many different types of high frequency miniature coaxial connectors used today that are available in different sizes and configurations with various limitations on maximum frequency transmission. Usually, the smaller the diameter of the connector, the higher the frequency signals that the connector is able to deliver successfully to the receiving medium. Some of the known connectors with notably small diameters are miniature coaxial connectors within the sub-miniature category known as SMA, SMB, and SMC. Among these, two of the most commonly used high frequency connectors are the SMA and the SMB wherein the former uses a threaded coupling means while the latter uses a snap-on coupling means. The snap-on coupling mechanism of the SMB connector is usually established with a metal collet within a first connector element engaging in a groove of a second connector element.
One of the primary aspects in determining the quality of a miniature coaxial connector is its working frequency range, more specifically how wide the frequency range can be so that it can be suitable for numerous applications. Generally, the working frequency range depends on a combination of factors such as the characteristic impedance, the Voltage Standing Wave Ratio (VSWR), and the connector cut-off frequency. These factors are significantly dependent on the internal structure and geometry of the connector where a mismatch or any sort of discontinuity may affect signal quality, especially in the higher frequency ranges.
Typical working frequency range of an SMB connector is up to 4 GHz while that of an SMA connector may be up to 26 GHz. Such lower working frequency range of the SMB connector as compared to that of the SMA connector may be due to shorter wavelength electromagnetic (EM) waves in the higher frequency range that can easily leak through the slots of the metal collet of the SMB connector or inciting unwanted modes of EM waves that inhibit proper signal propagation at those slots. In other words, the slots of an SMB connector may cause mismatches and other discontinuities in the internal structure. In contrast, the threaded coupling mechanism of the SMA connector minimizes the presence of little gaps and seams, and thus the structural mismatches and discontinuities at the junction where the two connector elements mate.
The choice of using an SMA connector or an SMB connector depends on the application. If the application requires more of the quick and easy connection method over signal propagation in the higher frequency, then the SMB connector type would be chosen over the SMA connector type. If the connector needs signal propagation in the higher frequency and does not have to undergo numerous cycles of engagement/disengagement, the SMA would typically be chosen over the SMB connector.